全文获取类型
收费全文 | 5517篇 |
免费 | 629篇 |
国内免费 | 4篇 |
专业分类
6150篇 |
出版年
2021年 | 74篇 |
2020年 | 57篇 |
2019年 | 54篇 |
2018年 | 75篇 |
2017年 | 63篇 |
2016年 | 68篇 |
2015年 | 141篇 |
2014年 | 124篇 |
2013年 | 241篇 |
2012年 | 249篇 |
2011年 | 245篇 |
2010年 | 153篇 |
2009年 | 162篇 |
2008年 | 213篇 |
2007年 | 193篇 |
2006年 | 212篇 |
2005年 | 188篇 |
2004年 | 168篇 |
2003年 | 151篇 |
2002年 | 154篇 |
2001年 | 167篇 |
2000年 | 168篇 |
1999年 | 162篇 |
1998年 | 73篇 |
1997年 | 68篇 |
1996年 | 72篇 |
1994年 | 63篇 |
1992年 | 116篇 |
1991年 | 113篇 |
1990年 | 119篇 |
1989年 | 129篇 |
1988年 | 110篇 |
1987年 | 100篇 |
1986年 | 85篇 |
1985年 | 76篇 |
1984年 | 88篇 |
1983年 | 84篇 |
1982年 | 60篇 |
1981年 | 80篇 |
1980年 | 56篇 |
1979年 | 90篇 |
1978年 | 71篇 |
1977年 | 61篇 |
1976年 | 66篇 |
1975年 | 55篇 |
1974年 | 67篇 |
1973年 | 59篇 |
1972年 | 52篇 |
1971年 | 53篇 |
1969年 | 59篇 |
排序方式: 共有6150条查询结果,搜索用时 0 毫秒
81.
Generation of asymmetry and segregation of germ-line granules in early C. elegans embryos 总被引:14,自引:0,他引:14
Germ-line granules in C. elegans embryos (P granules) can be visualized by immunofluorescence microscopy using a monoclonal antibody. In mutant zygotes with abnormal spindle orientations and in wild-type zygotes treated with the microtubule inhibitors nocodazole, colcemid, vinblastine, and griseofulvin, both P-granule segregation to the posterior pole and the concomitant pseudocleavage occur apparently normally, but the normally concurrent migration of the pronuclei is inhibited. Conversely, treatment of wild-type embryos with the microfilament inhibitors cytochalasins D and B inhibits P-granule segregation and pseudocleavage, as well as other manifestations of polarity, without preventing pronuclear migration. The results suggest that P-granule segregation does not require either the spindle or cytoplasmic microtubules, but that this process as well as generation of other asymmetries does require cytoskeletal functions that depend on microfilaments. 相似文献
82.
Activity of lysosomal cysteine proteinase during differentiation of rat skeletal muscle. 总被引:6,自引:0,他引:6 下载免费PDF全文
Cysteine-proteinase activities were measured in extracts of pre- and post-fusion populations of rat myogenic line L6 cells and in extracts of whole rat muscle. Activities of cathepsins B, L and H were compared. The substrates used included Z-Phe-Arg-NMec (cathepsins B and L), Z-Arg-Arg-NMec (cathepsin B), and Arg-NMec (cathepsin H) (where Z = benzyloxycarbonyl, and NMec = 4-methyl-7-coumarylamide); the enzyme activities were more specifically differentiated by appropriate concentrations of the inhibitors Z-Phe-Phe-CHN2 (CHN2 = diazomethane), bestatin and E-64 [L-trans-epoxysuccinyl-leucylamido(4-guanidino)butane]. These experiments have demonstrated the feasibility of determining the cysteine-proteinase activities of myoblasts from a single (60 mm-diameter) Petri dish, with enzyme concentrations in the range of 5-20 ng/ml. Specific activities of the enzymes in L6 cells increased 2-20-fold after fusion. Concentrations of cysteine proteinases in extracts from cultured myoblasts were two orders of magnitude greater than those in muscle-tissue extracts. Cultured-cell extracts contained endogenous inhibitor(s) to purified rat cathepsins B, L and H. 相似文献
83.
E L Lien L Ellenbogen P Y Law J M Wood 《Biochemical and biophysical research communications》1973,55(3):730-735
Chicken brain Arylsulfatase A (E.C.3.1.6.1) was immobilized by interaction with Concanavalin A. The immobilized enzyme retained its catalytic activity and this enzyme can be reused without appreciable loss of activity. The storage stability of bound and soluble enzymes was comparable and binding of enzyme to Concanavalin A increases its thermal stability. Kinetic studies indicated that bound enzyme shows similar anomalous kinetics as that of free enzyme but slight change was observed in relation to pH optima, Km value and activation energy. 相似文献
84.
L A Engel H Menkes L D Wood G Utz J Joubert P T Macklem 《Journal of applied physiology》1973,35(1):9-17
85.
T M Wood 《Biochimica et biophysica acta》1969,192(3):531-534
86.
87.
The effect of posture on maternal capillary blood Po2 and Pco2 was studied in pregnant and non-pregnant women. There was a significant decrease of Po2 (mean 13·0 mm. Hg) and significant decrease of Pco2 (mean 2·4 mm. Hg) when pregnant women sat up, but these changes did not occur in the non-pregnant. These findings may be relevant to debate on the optimum posture for labour. 相似文献
88.
89.
Some metabolites of 1-bromobutane in the rabbit and the rat 总被引:2,自引:2,他引:0
Sybil P. James D. A. Jeffery Rosemary H. Waring P. B. Wood 《The Biochemical journal》1968,109(5):727-736
1. Rabbits and rats dosed with 1-bromobutane excrete in urine, in addition to butylmercapturic acid, (2-hydroxybutyl)mercapturic acid, (3-hydroxybutyl)mercapturic acid and 3-(butylthio)lactic acid. 2. Although both species excrete both the hydroxybutylmercapturic acids, only traces of the 2-isomer are excreted by the rabbit. The 3-isomer has been isolated from rabbit urine as the dicyclohexylammonium salt. 3. 3-(Butylthio)lactic acid is formed more readily in the rabbit; only traces are excreted by the rat. 4. Traces of the sulphoxide of butylmercapturic acid have been found in rat urine but not in rabbit urine. 5. In the rabbit about 14% and in the rat about 22% of the dose of 1-bromobutane is excreted in the form of the hydroxymercapturic acids. 6. Slices of rat liver incubated with S-butylcysteine or butylmercapturic acid form both (2-hydroxybutyl)mercapturic acid and (3-hydroxybutyl)mercapturic acid, but only the 3-hydroxy acid is formed by slices of rabbit liver. 7. S-Butylglutathione, S-butylcysteinylglycine and S-butylcysteine are excreted in bile by rats dosed with 1-bromobutane. 8. Rabbits and rats dosed with 1,2-epoxybutane excrete (2-hydroxybutyl)mercapturic acid to the extent of about 4% and 11% of the dose respectively. 9. The following have been synthesized: N-acetyl-S-(2-hydroxybutyl)-l-cysteine [(2-hydroxybutyl)mercapturic acid] and N-acetyl-S-(3-hydroxybutyl)-l-cysteine [(3-hydroxybutyl)mercapturic acid] isolated as dicyclohexylammonium salts, N-toluene-p-sulphonyl-S-(2-hydroxybutyl)-l-cysteine, S-butylglutathione and N-acetyl-S-butylcysteinyl-glycine ethyl ester. 相似文献
90.
The bacterial degradation of catechol, 3-methylcatechol, 2,3-dihydroxy-β-phenylpropionic acid, and protocatechuic acid has been studied in detail. From the results obtained a general sequence has been proposed for the microbial oxidation of dihydroxy aromatic compounds. 相似文献